johnson r



Dec. 28, 1943. M. J. JOHNVSON Re. 22,414

MEASURING OR GAUGE DEVICE Original Filed Feb 15, 1940 2 Sheets-Sheet l Manfr l Johnson Dec. 28; 1943. M. J. JOHNSON 22,414

Y MEASURING on GAUGE DEVICE:

Original Filed Feb. 15, 1940 2 sheets-sheet 2 INVEN R Ma nfred I? Jolmsoh 2 T Q P Reiuued Dec. 28, 1943 MEASURING OB GAUGE DEVICE Manfred J. J ohnson, New Haven, Conn assignor to J-B-T Instruments, Inc., New Haven, 001111., a corporation oiConnecticut Original No. 2,258,113, dated October 1,1941,

Serial No. 319,107, February 15, 1940. Application for reissue October 3, 1942, Serial No.

19 Claims.

The present invention relates to a measurin device, and, mor particularly, to a device for detecting slight physical changes from a standard measurement.

An object of the present invention is to provide a measuring device or gauge which will be very sensitive and indicate slight changes from a standard, while at the same time being capable- 01 use through various ranges of changes. This is accomplished, according to the present invention. by positioning an armature in a normally balanced magnetic circuit and unbalancing the circuit in accordance with the change in a workpiece from a predetermined standard so a to produce a flux having a direction and magnitude depending upon said change, which flux reacts with the armature to cause a. predetermined movement thereof and thus indicat the extent of change in the workpiece from a standard.

While the method producing a balanced magnetic field and unbalancing the same in accordance with the change of a condition may take many forms, in the preferred embodiment of the present invention a pair of soft iron pole pieces are positioned so as'to provide an air gap to receive the current-carrying armature. A permanent magnet is disposed midway between the two soft iron pole pieces so as to produce a balanced magnetic circuit in which no flux passes through the air gap to react with the current-carrying armature therein. The permanent magnet is connected to a work-engaging member which, upon detection of a change from the standard in the workpiece, will cause th magnet to be moved from its mid .position and toward the soft iron pole pieces and unbalance the magnetic circuit, whereupon a flux will flow through the air gap in accordance with the extent and direction. oi

movement of the permanent magnet. Thi flux will react with the current-carrying armature and cause the same to rotate in accordance with the direction and amount of flux in the air gap. An indicator maybe connected to the armature relatively stationary work-engaging member which is adjustable toaccommodate for workpieces of various dimensions whereby the instrument can be used for a wide range of measurements.

In order to prevent the needle from fluctuating too rapidly, upon detection of a chang from the standard, the present invention provides a damping device for retarding movement of the needle.

The clamping effect becomes greater, according to the present invention, as the needl moves towards the ends of the scale.

Other features and advantages will be apparent from the specification and claims, when taken in connection with the drawings, in which:

Figure 1 shows a longitudinal sectional view of the device of the present invention.

Fig. 2 shows a sectional view, taken along lines Y is very sensitive and is particularly adaptable for and cooperate with a scale to indicate the extent and direction of change from the standard.

A feature of the invention resides in the adaptability of the instrument for a'larg number of measurements. This is accomplished by providing a circuit for the armature and controlling the current therein so as to vary the effect of the flux flowing through the air gap on the armature so as to cause more or less rotation of the armature, and, consequently, for or pointer.

Another ieatureoi the invention resides in the movement of the indicadetecting in the piece to be measured small phy ical changes from a standard.

In the preferred embodiment of the present invention, the instrument comprises a base l0 upon v which is mounted a pair of soft iron pole pieces ll, [2. A shown in Fig. l, the pole pieces are supported in spaced relation by being clamped between .the legs of a pair of U-shaped plates l8, ll, of brass or other nonmagnetic material, each of which has a flange l5 secured to the base by screws or the like.

The pole pieces are provided with portions l I a, Ila, intermediate their ends and projecting toward one another to form a substantially cylindrical air gap [6, as shown in Fig. 2, for receiving a cylindrical armature II.

The armature includes a current-carrying coil I9 rotatably disposed about a fixed core IS. The core is held in place by rings 22 as is well known in the art. While the armature may be mounted in many 'ways, in the illustrated form of the invention a pairoi posts 28 is secured to each of the plates l3 and i4 and project therefrom. The

free ends of the posts are connected by transversely extending plates 2 l Each plate is insulated from the posts and is inafter be described.

which isthreaded a bearing "for rotatably receiving and supporting an end of the armature shaft 24. Preferably, a jewelled bearing is used in order to reduce friction and secure a smoother operation of the armature The armature is normally held with its coil in a predetermined position with respect to the pole pieces- In the illustrated form of the invention, I have shown the coil 19 as being in alignment with the portions I la, 12a so as to obtain a maximumreaction when a magnetic flux is set up in the air gap. To 50 hold the armature in this position and yet permit it to rotate in either direction as required, I have provided a pair of helical springs 25, disposed one at each end of the shaft, These springs have one end secured to the shaft and the other end secured to an arm 26 carried by the. plate 2|, and are clamped thereto by means of a friction, washer 2! locked in place by a nut 28.

Thesehelical or torsion springs can also be used as a means for connecting the movable coil in an electrical circuit. For this purpose, the ends of the spring adjacent the shaft are connected to the ends of the coil and the other ends of the springs are connected through conductors 29, 30 to a circuit for controlling the amount of current in the armature coil, for the purpose as w ll here- This circuit'includes a source of energy or battery 3|, a variable resistance 32, and a milliammeter 33 for indicating the amount of current flowing in the circuit.

As shown in Fig. 2, a' U-shaped permanent magnet '35 is. mounted on the base with the ends thereof disposed between the pair of spaced pole pieces. Thev magnet is mounted on a torsion shaft 36 which has its ends adiustably supported apost 38 mounted on the base. The torsion shaft,

the soft'iron pole pieces represent the four legs of the bridge. When the permanent magnet is in the midposition, the magnetism of the circuit is balanced and no flux flows between the pole pieces through the air gap. 7 However, upon movement of the permanent magnet from its midposition, in either a clockwise or counterclockwise direction, it will, as it approaches the ends of the soft iron pole pieces, in effect, change the opposing branches of the bridge to cause an unbalance to exist and flux will flow through the air gap to be measured or gauged. To effect such a measurement, the permanent magnet is connected to a work-engaging element 45 so as'to be moved thereby. While the work-engaging element may take many forms, in the preferred form of the invention, it comprises an L-shaped lever projecting from the side thereof and having a work-engaging point 46. This point is adj justably and removablymounted thereon and should consist of a hardened steel point, a jewel or other suitable hard work-engaging surface.

is secured in the yoke by setscrews 38 threaded in v the yoke, and, by properly adjusting the position F When the permanent magnet is disposed in the position shown in Fig. 2, wherein its endsare magnetically equidistant from each of the ,pole' pieces, the magnet circuit, including the pole pieces, will be balanced and still no fluxwili flow in the air gap. However, the slightest movement of the permanentmagnet from the central position in either a clockwise or a counterclockwise. direction will cause the ends thereof to movecloser to the opposite ends of the pole pieces and reduce the air gap therebetween. This will cause an unbalanced condition to exist, whereupon a flux will flow between the portions Ha, lid; The

' amount of flux and its direction of flow are dependent upon thedirection and extent of movement of the magnet. This sets up a field in the air gap which will react with the field set up by the current-carrying armature and cause the same to rotate a distance dependent upon the amount of flux in the gap. The armature has.

mounted thereon an indicator needle 40 which cooperates with a scale 4| to indicate the amount of movement of the armature. A suitable counterbalance 42 can be provided on the needle if desired.

This system may be considered as analogous to -awheatstone bridge in which the four ends of Cooperating with this movable work-engaging member is a relatively stationary work-engaging member 41. These two work-engaging members may take many forms. For example, they may comprise a caliper for engaging either the inside or outside of an object to be-measured, or any other similar type of gauge point.

In the illustrated form of the invention, the

stationary member is shown as a platform sup-' ported on an extension Illa of the base by a pinrality of posts 49 slidably mounted in the base.

The-center of the platform has depending therefrom a rack 50. The base has a shaft 5| rotatably. mounted therein carrying at one end a pinion 52 which cooperates with the rack. A handwheel 53, is mounted on the shaftat the free end thereof. By rotating the handwheel, the work-supporting platform can be raised or lowered.

As was previously mentioned, the torsion shaft v is positioned between the work-supporting table and the w0rk-engaging member. The-work-supporting table is then adjusted until the permanent magnet is moved against the torsion shaft and into the position shown in Fig. 2. wherein it is equally spaced from either of the pole pieces. This will cause the balanced condition tq exist in the magnetic circuit, and the armature will assume its normal position and 'the indicator will point to zero on the scale and establish a standard of measurement against which the various workpieces canbe checked. r

- The Johanson gauge block is then removed and the workpieces, .which are to be checked or measured, are'then placed on the work-supporting table under the work-engaging member. If

,. the workpiece is of proper dimension, the permanent magnet will assume the position shown. in Fig. 2, and'the needle'will indicate no change undue vibrations of the needle.

can;

from the standard. However, should the workpiece be underslze, then the magnet would move counterclockwise, as shown in Fig. 4, and would cause the armature to be rotated and move the needle to indicate the amount of change from the standard.

Conversely, if the piece is oversize, then the permanent magnet will take up the position shown in Fig. 'and cause the unbalance of the magnetic circuit to produce a flux in the air gap and cause the armature to rotate in the direction to move the needle across the scale in the opposite direction. I

If desired, means may be provided for damping the movement or the armature to prevent the same from undue movement during the measurements. is preierably a device which operates in accordance with the movement of the armature and may be an air vane orother such damping means.

In the illustrated form of the invention, the. damping device comprises a U-shaped magnet 55 secured to the base by a pair of brackets 58 to extend upwardly in spaced relation with the pole pieces and armature II. A damping armature 51 including a coil 51a is mounted by a shaft 58 betweerithe poles of magnet 55 in a manner similar to the armature [1. While the armature 51 may be directly connected to the shaft 24 to be rotated thereby, it isherein shown as. being connected to the armature for movement thereby by an arm 59 having one end secured to the shaft 58 and has the other end Gil forked so as to extend around the indicator 40 to be driventhereby. It will be seen, therefore, that when the indicator moves to the right or left, it will, through its cooperation with the arm II, cause the armature to rotate in the magnetic field and set up a braking action to retard As is shown in Fig. 2, a pair of scales are provided to cooperate with the indicating needle, and the instrument can be regulated so that either of the scales can be used. In order to change the sensitivity of the instrument, the present invention has provided a means for controlling the amount of current in the armature 0011 I9; which reacts with the flux in the air gap. By adJusting the value of the current therein, more or less reaction wilibe obtained between the flux in'the 'air gap and the field set up by the currentin the coil, and the'pointer can be made' to move various extents .ior a given amount of;

flux passing through the air gap- In calibrating the instrument, the proper current value for the scaleA is determined and the milliammeter marked with a; line indicating the value of the current --which must be in the coil when scaleAisuscd; 1

Another line can be madapn the milliammeter to indicate the value of current necessary in the. I coil when scale B is usedg-n will be'seen, therefore} that the instrument. of the present invention can be quickly and easily adjusted to measure accurately changes over a wide range of values.

In actual practice, theinstrument has detected changes from a standard measurement to the extent of sixteen parts in a million.

.If desired, the instrument can be enclosed in a suitable casing 10, as shown in Fig. 1. The casing illustrated has a slot ll positioned above the indicating, needle and through which it projects and a wall 12 located behind the projecting needle to receive and support the scale 44. A cover ll having a transparent window II is mounted on the casing to enclose the needle and scale. The front portion or the casing is provided with a sloping surface lli upon which is mounted the rheostat 32 and milliammeter 33 for the armature circuit, these devices being so positioned on the casing that adjustments of the current in the armature circuit can be readily made while the instrument is in position to be used.

I desire it 'to be understood that I may make changes in the construction, combination and arrangement or the several parts, providing that such changes fall within the scope of the appended claims. a

I ciaim:

i. A measuring device comprising means for producing a balanced magnetic field wherein substantially no flux flows in an air gap therein; an armature in said air gap having a current of predetermined magnitude therein; an indicator connected to said armature; and means for un-' balancing said magnetic field in response to a.

change in measurement from a standard whereby a predetermined fiux will react with said armature to cause a movement thereof proportional to the unbalance of the field to indicate the ex tent and direction of said change.

2. A, measuring device comprising means for producing a balanced magnetic field wherein substantially no flux fiows in an air gap therein; an armature in said air gap having a current of predetermined magnitude therein; an indicator connected to said armature; means for unbalancing said magnetic field in response to a change in measurement from a standard whereby a predetermined flux will react with said arma ture to cause a movement thereof proportionalto the unbalance of the field to indicate the extent and direction of said change; and means for varying the current in the armature circuit to change the reaction between the armature and flux flowing in the air gap to regulate the extent of the movement of the indicator for a given change in measurement from a standard.

3. A measuring device comprising means for N producing a balanced magnetic field in an air gap; an armature in said air gap having a current of predetermined magnitude therein; an indicator connected to said armature; means for uhbalancing said magnetic field in response to a change in measurement froma standard whereby a predetermined-fluxwill react with said arma- Y ;,ture'to' causeja movement thereof-proportional to the unbalance of the field to indicate the extent .and direction of said change; and means for if changing the extent of movement of said armature for a given change in measurement.

'; 4. A measuring devicecomprising a balanced v magnetic. field; an armature in'said-fleld having. 'a currentof.predetermined magniture':'therein; p v indicator connected to said armatuie; a plw- ;rality ofscales cooperatingwith saidindicator; means for unbalancing said magnetic field in response to a changein measurement from a standard whereby-a predetermined flux will re-,

act with said armature to cause a movement.

thereof proportional to the unbalance of the field to indicate the extent and direction of said change; means for varying the current in said armature circuit to change the reading from one scale to another: and means for indicating when the proper value of current for either scale is flowing in the armature circuit. I

5. A measuring device comprising a from having a pair of pole pieces mounted thereon so ing armature mounted in t e gap; a permanent magnet yieldably mounted in a predetermined position between the pole pieces to produce a balanced magnetic held so that no flux passes through the air gap wherein the armature is positioned; means for shifting the. position oi the magnet'with'respect to the pole pieces in response to a change from a standard to produce an unbalance in the field and cause a flux to pass it through the air gap in either direction according to the direction-and extent of change, said flux reacting with the armature to cause moveanced magnetic field wherein no flux passes through the air gap wherein the armature is po sitioned; means for shifting the position of the I V a 99,414

as to form a gap therebetw I a current carrysaid members to a predetermined standard;

- means for indicating a change from said standmagnet with respect to the pole pieces in response to a change from a standard to produce an unbalance in the field and cause a flux to pass through the air gap in either direction according to the direction and extent 01' change, said flux reacting with the armature to cause movement thereof in either direction in proportion to the unbalance of the held; an indicator on said armature for indicating the direction and extent of change; and means for varying the current in the armature to change the amount 01' reaction of the flux in the air gap thereon and the extent of movement of the indicator for a predetermined change from a standard.

7. A measuring device comprising a frame having a pair of pole pieces mounted thereon so as to form a gap therebetween; a current-carrying armature mounted in the gap; aper'manent magnet yieldably mounted in a predetermined 7 position between the pole pieces to produce a bal anced magnetic field wherein no flux passes through the air gap wherein the armature is positioned; work-engaging means connected to the a magnet for shifting a position of the magnet with respect to the pole pieces in response to a change from a standard to produce an unbalance in the field and cause a flux to pass through the air gap'in either direction according to the direction and extent of change, said fluxreacting with the armature to cause movement thereof in either direction in proportion to the unbalance oi the field: and an indicator on said armature for indicating the direction and extent of change. '8. A measuring device comprising a pair of work-engaging members; means for adjusting said members to "a predetermined standard; and

means for indicating a change from said stand-' ard comprising a balanced magnetic circuit wherein no fluxiiows in an air gap therein. an armature in said air gap, means connected to one of said work-engaging members for unbalancing said magnetic circuit to produce a flux in said air gapof a magnitude and direction, dependent upon the magnitude and direction of the change from said standard, to react with said armature and cause movement thereof, and means for indicating such movement. 1 Y

Y 9. A measuring device comprising a pair of work-engaging members; means for adjusting ard comprising a balanced magnetic circuit wherein no flux flows in an air gap therein, an

armature in said air-gap, means connected to one of said work-engaging members for unbalanci'ng' upon the magnitude and direction of the change from said standard, to react with said armature and cause movement thereof, and meansfor indi'cating such movement:-and separate spaced braking means connected to said armature for damping movement or said armature.

10. A measuring device comprising a pair of work-engaging members; means for adjusting said members to a predetermined standard; means for indicating a change from said standard comprising an armature provided with a coil having a predetermined current therein, a balanced magnetic circuit having an air gap wherein no flux flows, the armature being located in said air gap, means connected to one of said workengaging members for unbalancing said magnetic circuit to produce a flux in said air gap of a magnitude and direction, dependent upon the magnitude and direction of thechange from said standard, to react with said armature and cause movement thereof, and means for indicating such movement; and means for varying the current in said armature circuit to change the amount of reaction between thearmature and flux to produce more or'less movement oi the armature for a given change from the-standard.

11. A measuring device comprising a pair of work-engaging members; means for adjusting said members to a predetermined standard: means for indicatingm change from said standard comprising a balanced magnetic circuit wherein no flux flows in an air gap therein, an

' armature in said air gap, means connected to one oi said work-engaging members for unbalancing said magnetic circuittp produce a flux in said air gap or a magnitude and direction, dependent upon the magnitude and direction or the change from said standard, to react with said armature. and cause movement thereof, and means for indicating such movement; and means including a damping armature positioned in a separate magnetic field and driven by said first-named armar ture for damping the movement of said indicator.

12, A measuring instrument comprising a base: a pair of soft iron pole pieces mounted on the base, said pole pieces forming an armature-receiving air gap; an armature rotatably mounted in the air gap and normally urged into a predeenclosing the magnetic pole pieces and armature and having a scale thereon; and an indicator secured-to the armature and cooperating with the scale to indicate the amount of change from the standard. I

13. A measuring device comprising means for producing .a balanced field having an air gap wherein no flux flows, an armature mounted in said-air gap and adapted to react to flux in said gap, an indicator connected to the armature for sane movement thereby; and means for unbaiancing the magnetic field in response to a change in measurement from a standard whereby a predetermined flux will flow in said air gap and react with the armature to cause a movement of the armature proportional to the unbalance of the influenced by the direction and magnitude of the flux therein to produce an amplified indication of the extent and direction 01 the movement of pivoted in one of the air gaps and influenced by the direction and magnitude or any flux therein, and a permanent magnet extending between the other two air gaps and pivoted therebetween so as to be moved to vary the relative magnitude of its flux which enters the diflerent members at such two air gaps, such variation varying the condition in theair gap in accordance with the direction and extent of said changavthe flux in the air gap reacting with said armature to cause movement thereof in either direction in proportion to the variation of said flux condition; and

i an indicator moved by said armature for indieating the direction and extent of change.

16. A magnetic auging instrument comprising a pair of three-legged magnetic members with their legs extending to form three magnetic gaps, a permanent magnet having one of its poles positioned adjacent one or the gaps and its other pole positioned adjacent anothergap and. pivoted to turn to vary the distribution or its flux between the pole pieces forming such gap and thereby the direction and magnitude of its flux which passes across the third gap, and an armature pivotally mounted within the third gap and the permanent magnet from a given position.

17. A magnetic gauging device comprising a pair of magnetic members each having three projecting pole pieces forming three magnetic gaps, a permanent magnet mounted between two of the gaps and pivoted so as to be rotated in opposite directions from a position where its flux is ymmetrically distributed in the magnetic members forming a return path, an armature pivoted in the third gap and influenced by the flux therein, the direction and magnitude of the flux across the third gap varying as the permanent magnet is turned in opposite directions from a symmetrical magnetic distribution position.

18. A magnetic, gauging device comprising a pair of magnetic members magnetically separated by three air gaps, an armature member pivoted in one oi the air gaps and influenced by the direction and magnitude of any flux therein, and a permanent magnet extending between the other two air'gaps and rotatable about-an axis passing between the two air gaps so as to be moved to vary the relative magnitude of its flux which enters the different members "at such two air gaps, such variationyarying the flux through the armature air gap.

19. A magnetic gauging device comprising a pair of magnetic members separated by three magnetic air gaps in parallel relation, an armaaure pivoted in one of the gaps influenced by the direction and magnitude of any flux therein, a permanent magnet having a north pole adjacent one 01 the other gap and a south pol adjacent the remaining gap, said permanent magnet bein pivoted betweenits poles so that it may be turned through a smallv angle to, reverse the polarity of and vary the magnitude of the flux which it induces in said pair of magnetic members, thereby varying the direction and magnitude of the flux in the armature air gap, the angular deflection of the armature being large as compared to the angular movement of the permanent magnet. j

MANFRED J. JOHNSON. 

